Fluorine-containing surfactants or fluorine-containing surface modifiers are widely used as various coating materials, surface modifiers, and the like from the standpoint that they are excellent in terms of leveling property, wettability, permeability, anti-blocking property, slidability, water/oil repellency, stain-proof property etc.
Cured coating films obtained by applying and curing an ultraviolet-curable coating containing such a fluorine-containing surfactant or a fluorine-containing surface modifier (hereinafter abbreviated as “fluorine-containing surfactant or the like”) exhibit excellent surface properties. On the other hand, because of heating, humidity, exposure to a chemical such as an acid or an alkali, washing for removing stains, or the like, a part of the fluorine-containing surfactant or the like is easily detached or volatilized from the surfaces of the cured coating films, resulting in problems such as contamination in production lines and deterioration in the stain-proof properties of the surfaces of the coating films.
For example, in the field of coating materials for coating a protective film such as a triacetyl cellulose (TAC) film used in polarizers for liquid crystal displays, in order to provide a film surface with stain-proof properties for fingerprints and stains, a surface of the protective film is coated with an ultraviolet-curable hard-coating material containing a fluorine-containing surfactant or the like. However, in order to improve adhesiveness, a saponification treatment (strong alkali treatment) is performed on a surface of the protective film, the surface being opposite to the surface having the hard-coating material thereon. In this step, contact between the hard-coated surface and a saponification solution is inevitable, and thus the fluorine-containing surfactant or the like present in a surface layer is decomposed by a strong alkali, resulting in deterioration in the stain-proof properties.
Furthermore, as a coating/ink or a black resist for a black matrix or coloring materials for forming color pixels of three colors of red, green, and blue, the black matrix and the coloring materials being used for a color filter for liquid crystal displays, ultraviolet-curable resin compositions containing a fluorine-containing surfactant or the like are used in order to improve liquid repellency after the formation of a coating film. However, in particular, when the black matrix is formed by patterning a resist, after curing by ultraviolet irradiation, a heat-setting treatment is conducted under a high-temperature condition, for example, at 230° C. for 30 minutes. Accordingly, a part of a component of the fluorine-containing surfactant or the like is volatilized from the surface. As a result, the liquid repellency of the surface decreases, and a problem such as contamination of other portions and production lines due to the volatilized substances occurs.
Known techniques for preventing such a decrease in the function of a coating surface include the use of a polymerization-type fluorine-containing surfactant containing an unsaturated group, the surfactant being obtained by copolymerizing a fluorinated alkyl group-containing monoacrylate with an active hydrogen-containing acryl monomer, and then polymerizing an isocyanate group-containing acryl monomer with the resulting polymer (refer to, for example, Patent Document 1), and the use of a perfluoropolyether group-containing urethane acrylate as a fluorine-containing surfactant, the perfluoropolyether group-containing urethane acrylate being obtained by allowing a hydroxyl group-containing perfluoropolyether and a hydroxyl group-containing acryl monomer to react with a triisocyanate compound which is a trimer of a diisocyanate (refer to, for example, Patent Document 2).
However, in the polymerization-type fluorine-containing surfactant described in Patent Document 1, since a fluorinated alkyl group is bonded to a polymer chain in the form of a pendant, decomposition and detachment are still easily caused by the above-mentioned strong alkali treatment, and the stain-proof properties tend to deteriorate. In particular, once stains adhere, the stains cannot be easily removed by wiping, and it is very difficult to remove such stains. In particular, when a coating film is cured by irradiation of ultraviolet rays in air, such a polymerization-type fluorine-containing surfactant tends to be subjected to an effect of curing inhibition caused by oxygen because the surfactant is present on a surface of the coating film. In addition, in the above-mentioned applications, the irradiation time of ultraviolet rays tends to be decreased in order to increase the production rate. Therefore, it is very difficult to allow the polymerization-type fluorine-containing surfactant to sufficiently react with a coating film-forming component, the polymerization-type fluorine-containing surfactant remains on the surface of the coating film in an unreacted state, and thus the surfactant is easily removed. As a result, the stain-proof properties tend to decrease, resulting in a serious problem that, once stains adhere, the stains are not easily removed. On the other hand, in the perfluoropolyether group-containing urethane acrylate described in Patent Document 2, it is difficult to allow the hydroxyl group-containing perfluoropolyether and the hydroxyl group-containing acryl monomer to react with the trifunctional isocyanate compound in an appropriate ratio. Consequently, a compound having only a perfluoropolyether and a compound having only an acryloyl group are produced in a large amount. Therefore, it is difficult to industrially produce the perfluoropolyether group-containing urethane acrylate.    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2007-246696    [Patent Document 2] Japanese Patent No. 3963169